The present invention relates to a video information recording/reproduction system for recording video information composed of digital video information on a disk storage medium and reproducing video information from the disk storage medium.
In recent years, recording/reproduction systems for recording and reproducing so-called multimedia information such as digital video information or still image, audio information, and character information are extensively developed. Particularly, a DVD (Digital Video Disk) drive using a DVD as a storage medium has received a great deal of attention. The DVD drive includes a read-only DVD-ROM drive and a DVD-RAM drive which allow recording and reproduction.
In particular, the DVD-RAM drive has not only a function of reproducing multimedia information recorded on the DVD in advance but also a function of recording digital video information transmitted from, e.g., a digital broadcasting station. The DVD-RAM drive has therefore received attention as not only a video player or videocassette recorder for reproducing video information on the screen of a television receiver but also an external storage device for a personal computer. The DVD-RAM drive is a promising storage medium incorporated in an apparatus such as a set top box or IRD (Integrated Receiver Decoder) which has a digital satellite broadcasting receiver (including an antenna) and displays received digital video information on the display (screen) of a television receiver or personal computer.
Using the recording/reproduction function of the DVD-RAM relatively easily realizes an edit function of editing video information recorded on the DVD-RAM. The video information edit function is to cut (remove) desired frame information included in full-motion video continuously reproduced on the screen of the television receiver or the like, and to extract desired frame information into another video information. Realizing this edit function requires a function capable of editing desired frame information in full-motion video in units of frames (or units of pictures) designated by the user.
Video information recorded on the DVD-RAM is generally encoded (compressed) by a moving picture coding scheme called MPEG (Moving Picture coding Experts Group) 2. This MPEG2 scheme employs a so-called GOP (Group Of Pictures) structure. The GOP structure is used to process video data as an access unit obtained by grouping a plurality of pictures (frames), and is generally composed of about 15 frames (reproduction time: about 0.5 sec).
One GOP is composed of a predetermined number of pictures of a plurality of picture types (to be referred to as picture data hereinafter). The picture type means the type of encoded image and includes three types of pictures, i.e., an I picture (Intracoded image), a P picture (Predictive coded image), and a B picture (Bidirectionally predictive coded image). The I picture is frame information which can be decoded independently of another type of picture data (without any preceding and succeeding frame information). The P picture is frame information which can be decoded using difference information from the I picture. The B picture is frame information which can be decoded using difference information from the preceding I picture and difference information from the succeeding P picture. That is, the P and B pictures except for the I picture are encoded images which cannot be decoded by themselves.
As described above, editing digital video information using the DVD-RAM requires a function capable of editing the information in units of frames (or units of pictures) designated by the user. However, in the recording/reproduction system employing the MPEG2 scheme, when the video data process unit (i.e., coding unit) is the GOP, a position within the GOP may be designated as a reference position for dividing video information. More specifically, when video information (continuous reproduction data unit including a GOP header) composed of a plurality of GOPs is divided at a desired position, a picture within a given GOP may be designated as a division boundary.
The GOP is composed of a plurality of picture types of picture data, as described above. When, e.g., the former half of video data is cut (removed) at a designated division position, the start picture in the latter half of the video data may be a P or B picture. Since the P or B picture cannot be independently decoded, video information including the latter half of the video data causes a reproduction error. If the start picture is an I picture, the video information can be reproduced without any problem. Namely, in the system wherein video data is processed in units of GOPs, like the MPEG2 scheme, the data can be easily edited in units of GOPs but cannot be practically edited in units of pictures within the GOP.